Mercury Myths

The IFBB believe that the health benefits of eating fish and seafood outweigh any theoretical risks and urge U.K. dietary guidelines to revisit their advisory.

This belief is supported by a global consortium of scientists specialising in neuroscience and biochemistry including Professor Michael Angus Crawford, Imperial College London and Prof J. Thomas Brenna, Cornell University, who, at the Hawaii Seafood Symposium in 2010, made a public statement urging the US Food and Drug Administration (FDA) to make urgent changes to current fish-intake guidelines to include the benefits of fish and seafood consumption during pregnancy and throughout life.

The current advice from the UK Government Scientific Advisory Committee on Nutrition and the Committee on Toxicity makes recommendations to all Government agencies including the NHS, National Institute for Clinical Excellence, Food Standards Agency and Public Health England. The IFBB urges the UK to amend the following:

Amend the language used in the guidelines which says “All other adults, including breastfeeding women, should eat no more than one portion of oily fish per week. This is because these fish can contain more mercury than other types of fish, and can damage a developing baby’s nervous system.” The language used is negative and sounds like fish consumption is damaging to health.

The IFBB recommends at least two portions of oily fish should be consumed per week so this guidance should also be revised to say “Oily fish: if you are trying for a baby, or are pregnant or breastfeeding, you should have at least two portions of oily fish a week. A portion is around 140g.”

The IFBB also believes that it is crucial that the guidance on oily fish consumption emphasises the importance of adequate fish intake to brain development and health.

Why is fish consumption so important?

The nutritional benefits of fish consumption, especially during pregnancy, are well-documented. Fish and seafood contain high quality protein, essential omega-3fatty acids in addition to a wide-range of other nutrients such as vitamins A, B-complex, and D, iron, iodine, magnesium, zinc and selenium which are health promoting. Selenium for example is an important cofactor for antioxidants and is thus probably protective against methylmercury. It is also important to note that the nutrients in a portion of fish act together to facilitate absorption, whereas supplements only provide the fish oil. During pregnancy, essential fats such as the omega-3s, docosahexanoic (DHA) and eicosapentaenoic acids (EPA), play a critical role in foetal brain development. Furthermore, there is a preferential uptake of omega-3 from the mother across the placenta to the developing baby which increases during the last trimester, a process coined as biomagnification in the work of Professor Michael Crawford 1.

Despite the wide-spread scientific consensus on the essentiality of omega-3 highly unsaturated fatty acids during pregnancy, concern has been expressed over potential harm from mercury, polychlorinated biphenyls (PCB’s) and dioxins found in certain fish species. It is this fear which, despite almost two decades of research into populations with moderate fish intake (which have found no evidence of harm to neurodevelopment), is leading UK government health and nutritional advice.

What does the research say?

Researchers from the US National Institutes of Health in collaboration with Bristol University examined data from the Avon Longitudinal Study of Parents and Children (ALSPAC) to establish associations between maternal fish consumption and child developmental outcomes. The ALSPAC recruited over 15,000 women during pregnancy in the early 1990s and have charted the health and development of their children ever since. The results of this study were that low maternal omega-3 consumption from seafood was associated with suboptimal verbal IQ development in their children. In addition, low maternal seafood intake was associated with an increased risk of suboptimum outcomes for pro-social behaviour, fine motor, communication, and social development scores 2.

In another study published this year, the ALSPAC team further investigated whether prenatal mercury levels were associated with adverse child behaviour. In order to do this, they compared maternal total blood mercury in pregnancy with adverse behaviour as assessed by the Strengths and Difficulties Questionnaire (SDQ) at seven different time points between ages 4 and 16-17 years of age 3. They found no evidence to link levels of mercury with adverse child behaviour irrespective of whether or not the mother ate fish during pregnancy. The findings also supported results from The Seychelles Child Development Study Nutrition Cohort 2 4. In this study 1265 mother/child pairs were assessed during pregnancy and up to 24 years later. All mothers ate fish every day, and levels of mercury in these waters are similar to those in the UK, so that their exposure to mercury was 10x that typical in the UK. Yet this study reported no association between mercury exposure and child developmental outcomes at 20 months of age. These findings also supported earlier work by the same researchers (Nutrition Cohort 1) which found no evidence that higher mercury exposure was linked to adverse outcomes over the first 5 years of follow-up 5. Likewise Oken et al (2016) found no evidence for associations of prenatal mercury with any adverse cognitive outcomes 6. These studies have led researchers to suggest that the benefits of fish consumption outweigh and may even counter any potential adverse effects of mercury.

Conclusion

Thus since 2010, a global body of scientists has been actively promoting the benefits of seafood consumption to brain health and cognitive development to the US Food and Drug Administration and European agencies. In 2014, the FDA and Environmental Protection Agency (EPA) published draft dietary guidelines which revised their fish consumption policy to encourage pregnant women, those planning to become pregnant, breast-feeding mothers and young children, to consume more fish and a variety of fish from choices lower in mercury. Their key message is to eat 8-12 ounces of a variety of fish each week which translates to 2-3 portions of fish per week according to the child’s age and calorie requirements. In this revision they recognised that the nutritional value of fish is important during not only in the preconception period, but also for mother and breastfed babies and throughout childhood.

Much of the current UK guidance does not factor in the many health benefits of eating fish and seafood. The IFBB believe that this advice is confusing and likely to be misinterpreted leading to a decrease in fish and seafood consumption by mothers during pregnancy which, in turn, may contribute towards detrimental neurocognitive developmental outcomes. The IFBB recommend that a revision of the SAC guidance should be undertaken to reflect current evidence-based neuroscientific research as has already been done in the USA.

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